Highly spatial variation of soil microbial respiration and temperature sensitivity in a subtropical forest

Abstract

Quantifying the spatial variation and drivers of microbe-driven soil carbon (C) decomposition (also called soil microbial respiration, MR) and its temperature sensitivity (Q₁₀) is crucial for reducing the uncertainty in modelling the terrestrial C cycle under global warming. To this end, most previous studies sampled soils from multiple sites at regional scales and incubated them at the same temperature level in the laboratory. However, this unified incubation temperature is too warm to the cold sites, and too cold to the warm sites, thus causing a large bias in the MR and Q₁₀ estimations. Here, we conducted fine scale intensive sampling (194 soil samples) and measurements within a 4-ha subtropical forest plot to examine the underlying mechanisms driving the spatial pattern of MR and Q₁₀. Our results showed that both MR and Q₁₀ varied spatially within subtropical forests. The fine scale variation of MR was dominated by soil nitrogen concentration and slope position, and Q₁₀ was dominated by soil fungi abundance. Overall, the 35 investigated biotic and abiotic factors explained 38% of the spatial variation of MR and 9% of the spatial variation of Q₁₀ in the subtropical forest. This suggests that the fine scale variation of soil C dynamics is much more complex than that at the regional scale reported in previous studies, which should be considered in the assessments of terrestrial soil C cycles.

Keywords: Fine scale soil C decomposition; Spatial heterogeneity; Subtropical forest; Temperature sensitivity.